diff --git a/index.js b/index.js
index 0f4b28b4..38b393d6 100644
--- a/index.js
+++ b/index.js
@@ -1,17 +1,54 @@
 class SortedList {
-  constructor() {}
+  constructor() {
+    this.items = [];
+    this.length = 0;
+  }
 
-  add(item) {}
+  add(item) {
+    this.items.push(item);
+    this.items.sort((a, b) => a - b);
+    this.length = this.items.length;
+  }
 
-  get(pos) {}
+  get(pos) {
+    if (pos >= this.length) {
+      throw new Error("OutOfBounds");
+    }
 
-  max() {}
+    return this.items[pos];
+  }
 
-  min() {}
+  max() {
+    if (this.length === 0) {
+      throw new Error("EmptySortedList");
+    }
 
-  sum() {}
+    return this.items[this.length - 1];
+  }
 
-  avg() {}
+  min() {
+    if (this.length === 0) {
+      throw new Error("EmptySortedList");
+    }
+
+    return this.items[0];
+  }
+
+  sum() {
+    return this.items.reduce(
+      (total, number) => total + number,
+      0
+    );
+  }
+
+
+  avg() {
+    if (this.length === 0) {
+      throw new Error("EmptySortedList");
+    }
+
+    return this.sum() / this.length;
+  }
 }
 
 module.exports = SortedList;
diff --git a/package.json b/package.json
index 3a5127ae..4f04f20d 100644
--- a/package.json
+++ b/package.json
@@ -19,5 +19,8 @@
     "intro"
   ],
   "author": "fer@ironhack.com",
-  "license": "MIT"
+  "license": "MIT",
+  "devDependencies": {
+    "mocha": "^11.7.6"
+  }
 }